perf tools: Fixup module symbol end address properly

I got a strange error on ARM to fail on processing FINISHED_ROUND
record. It turned out that it was failing in symbol__alloc_hist()
because the symbol size is too big.

When a sample is captured on a specific BPF program, it failed. I've
added a debug code and found the end address of the symbol is from
the next module which is placed far way.

ffff800008795778-ffff80000879d6d8: bpf_prog_1bac53b8aac4bc58_netcg_sock [bpf]
ffff80000879d6d8-ffff80000ad656b4: bpf_prog_76867454b5944e15_netcg_getsockopt [bpf]
ffff80000ad656b4-ffffd69b7af74048: bpf_prog_1d50286d2eb1be85_hn_egress [bpf] <---------- here
ffffd69b7af74048-ffffd69b7af74048: $x.5 [sha3_generic]
ffffd69b7af74048-ffffd69b7af740b8: crypto_sha3_init [sha3_generic]
ffffd69b7af740b8-ffffd69b7af741e0: crypto_sha3_update [sha3_generic]

The logic in symbols__fixup_end() just uses curr->start to update the
prev->end. But in this case, it won't work as it's too different.

I think ARM has a different kernel memory layout for modules and BPF
than on x86. Actually there's a logic to handle kernel and module
boundary. Let's do the same for symbols between different modules.

Signed-off-by: Namhyung Kim <[e-mail]>
Reviewed-by: Leo Yan <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Mike Leach <[e-mail]>
Cc: John Garry <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

tools/perf/util/symbol.c

···
 		 * segment is very big.  Therefore do not fill this gap and do
 		 * not assign it to the kernel dso map (kallsyms).
 		 *
+		 * Also BPF code can be allocated separately from text segments
+		 * and modules.  So the last entry in a module should not fill
+		 * the gap too.
+		 *
 		 * In kallsyms, it determines module symbols using '[' character
 		 * like in:
 		 *   ffffffffc1937000 T hdmi_driver_init  [snd_hda_codec_hdmi]
 		 */
 		if (prev->end == prev->start) {
+			const char *prev_mod;
+			const char *curr_mod;
+
+			if (!is_kallsyms) {
+				prev->end = curr->start;
+				continue;
+			}
+
+			prev_mod = strchr(prev->name, '[');
+			curr_mod = strchr(curr->name, '[');
+
 			/* Last kernel/module symbol mapped to end of page */
-			if (is_kallsyms && (!strchr(prev->name, '[') !=
-					    !strchr(curr->name, '[')))
+			if (!prev_mod != !curr_mod)
+				prev->end = roundup(prev->end + 4096, 4096);
+			/* Last symbol in the previous module */
+			else if (prev_mod && strcmp(prev_mod, curr_mod))
 				prev->end = roundup(prev->end + 4096, 4096);
 			else
 				prev->end = curr->start;